3.4.4 Re-Record Inputs
Each coarse input level control has a further five positions in which it can
select signals for re-recording via the microphone input bus lines. There are ten of
these lines numbered 1A to 5A and 1B to 5B. The A series being available on the
left hand channel of each Microphone Cassette and the B series being available on
the right hand channel of each Microphone Cassette. These bus lines are fed at a
level of –10dBV from the outputs of Amplifiers A1 in the Track Monitor Cassettes,
line 1A, 1B, 2A and 2B coming from the extreme left Track Monitor Cassette, lines
3A, 3B, 4A and 4B coming from the next cassette and lines 5A and 5B coming from
the extreme right hand Track Monitor Cassette this being the one for use with the
Auxiliary Stereo tape machines.
Between each bus line and the corresponding stud on the input selector
control a 25dB loss resistive pad is inserted to reduce the level from –10 to –35dBV.
The fine gain control is available to give
±
5dB of fine adjustment of the level.
3.4.5 Test Input
The extreme anticlockwise position of each coarse input level control makes
connection with an oscillator bus line. The Oscillator is located in the Studio
Playback Cassette and, when the Oscillator level control is at 0, the level on this bus
line is –35dBV, this being the standard level at the point of injection.
3.5
Signal Path
3.5.1 Band Pass Filter
The output of each Amplifier D is connected to the input of a Band Pass
Filter, the circuit of which is described in 12.7. These contain adjust on test (AOT)
resistors whereby the overall frequency response of the channel is trimmed.
The output of the Band Pass Filter is at about –6V and is directly connected
to the input of the Compressor/Limiter. In order not to apply this potential to the
inject socket an a.c. coupling consisting of a 6.8
µ
F capacitor and 33k
Ω
resistor is
inserted.
3.5.2 Compressor/Limiter
This is described in 12.22. A 3-position locking key is provided in each
channel, the positions being marked “Out”, “Compress” and “Limit”. In the Out
position, the Compressor/Limiter is removed from the forward path but its input is
left connected so that its meter indicates the signal level.
A Third locking key is provided which is marked Gang. When this is set to
the forward position the two compressor/limiters are controlled by which ever of the
two control voltages is instantaneously the greater. When this is used the two other
keys should both be set to Compress or Limit. The hold and recovery controls are
coaxial. The recovery control is the lower of the two and is a stud switch with six
positions numbered 1 to 6. The recovery times corresponding to these positions are
approximately 0.1, 0.25, 0.5, 1, 2 and 5 seconds respectively. An approximate
calibration of the hold control which is a logarithmic 10k
Ω
carbon potentiometer is
marked on the panel. Normally the hold control will be adjusted prior to a take and
